1. Field of the Invention
The present invention relates to an idle air bypass arrangement, and more particularly to an arrangement for reducing noise resulting from air flowing from the idle air bypass passage, or other passage used to provide air at idle conditions.
2. Background Art
Generally, it is known to use an idle air bypass arrangement for internal combustion engines which utilize an air input system having an air inlet duct arranged to direct outside air to a throttle valve assembly for supply to in input manifold. Because the throttle valve is closed when an engine is at idle, such idle air bypass arrangements operate to selectively supply air to the engine when the throttle valve is closed. Typically, an idle air bypass valve is positioned in the induction system to circumvent air around the throttle plate so that air can pass through a narrow channel to the intake manifold at low engine speeds. The resulting high air velocity through the narrow channel produces high-speed air noise which is emitted via a downstream body/cavity/chamber such as the intake manifold or a throttle body spacer. The high-velocity noise, in turn, excites the surfaces of the chamber, which in turn results in radiated noise being generated from the exterior surfaces of the chamber.
In an attempt to reduce such noise, U.S. Pat. No. 5,947,082 to Choi et al. discloses positioning a separate silencer device between an outlet of the idle air bypass valve and the intake manifold. The silencer device is arranged to reduce air velocity flowing from the bypass valve into the intake manifold, thereby reducing noise generated therein.
While such arrangements operate to reduce noise levels, such arrangements require either upgrading of the entire idle air bypass passage effective area or utilization of a larger idle air bypass valve in order to maintain equivalent flow rates through the passage to achieve the associated minimization of noise levels.
Therefore, a need exists for an arrangement capable of reducing noise generated by air flow through an idle air bypass passage without otherwise restricting the flow of air through the passage.
As such, an object of the present invention is to provide an arrangement capable of reducing intake air noise which does not restrict the flow of air through an idle air bypass passage.
In accordance with this and other objects, a noise reduction arrangement is provided for an idle air bypass passage used to supply air to an engine, the idle air bypass passage having an air inlet for receiving a flow of air from an air intake duct and an air outlet coupled to a manifold on the engine to selectively allow a flow of air to bypass a throttle valve assembly connected to the engine, wherein the noise reduction arrangement includes an acoustic diverter positioned at the idle air bypass passage air outlet and arranged to limit sound waves generated by the air flowing through the bypass passage from traveling directly toward any exterior walls proximate the air outlet.
In accordance with one aspect of the present invention, the acoustic diverter is contoured relative to the flow of air exiting the bypass passage air outlet so as redirect the sound waves to travel toward an inner portion of the engine, such as a cylinder head mounted to the engine. In accordance with other aspects of the invention, the acoustic diverter can be fastened to the bypass passage air outlet or integrally formed as part of the bypass passage air outlet.
In accordance with yet another aspect of the present invention, a method is provided for reducing noise generated by air flowing through an idle air bypass passage used to supply air to an engine, wherein the idle air bypass passage includes an air inlet for receiving a flow of air from an air intake duct and an air outlet coupled to a manifold on the engine to selectively allow a flow of air to bypass a throttle valve assembly connected to the engine, the method including diverting sound waves generated by air exiting the idle air bypass passage air outlet to limit the sound waves from traveling directly toward any exterior walls proximate the air outlet.
With the acoustic diverter of the present invention, noise can be reduced without restricting the air flowing through the idle air bypass passage. In fact, airflow restriction can even be reduced by the present invention.
The above objects and other objects, aspects, features and advantages of the present invention are readily apparent from the following detailed description when taken in connection with the accompanying drawings.